Cable ties and other forms of tie strip are used to secure items together quickly and easily. Example uses include bundling cables, sealing bags or binding plants to stakes.
One conventional type of tie strip is a long thin plastic device, with an apertured head at one end, extending from which is a slimmer tail portion. On insertion of the tail portion into the aperture of the head portion, the head engages with one of a series of latches spaced along the tail, and thereby prevents its withdrawal. A closed loop is thus formed by the strip which may be pulled tight around target items to fasten them together.
One significant disadvantage of such a tie strip is that the tail portion pulled through the head during fitting is wasted, because it performs no function and cannot be re-used. Only the tail portion forming the closed loop finds utility.
Another major disadvantage of conventional tie strips is their constrictive nature. Such tie strips are readily tightened, but do not allow the enclosed items any room to grow, expand or deform.
An alternative tie strip that reduces waste is found in prior art DE 2,524,013 which discloses a tie consisting of a plurality of apertured cells.
However, in any tie strip composed of a repetition of unit cell portions, the transverse width of the strip will always exceed the relative transverse width of the unit cells' apertures. In order to form a closed loop it is therefore necessary either to reduce the width of the strip and/or to increase the width of the apertures.
The form of tie strip described in DE 2,524,013 solves this problem by placing apertures substantially longitudinally along the strip that are longer than the strip is wide. The strip may then be inserted through itself at any aperture point by twisting the front end of the strip through 90°. The tie can then be pulled around the target items and secured in place by a reverse twist of 90°. The unused tail portion of this tie strip can then be used again, if it is long enough, thereby greatly reducing waste.
Alternatively, prior art U.S. Pat. No. 3,438,095 uses a similar design of cell, but without the need for any twisting, relying instead on applied force and material deformation to achieve threading.
Other alternative waste-reducing tie strip concepts are found in U.S. Pat. No. 3,913,178 and U.S. Pat. No. 4,150,463 wherein a continuous flat strip narrows by virtue of being foldable along its longitudinal axis, and utilises punched barbs along the centre of the strip which engage with the residual apertures formed from other such punched barbs on other portions of the strip, preferably once the tie is in a folded state. No longitudinal deformation is possible.
Another alternative tie strip is found in the inventor's earlier U.S. Pat. No. 5,799,376. This tie is also formed from a plurality of apertured cells, but threading is achieved by the use of bendingly deformable spring portions extending from the strip. These allow cells to expand and/or contract to facilitate passage.
This form of tie strip not only reduces waste, but also incorporates some longitudinal expansion by virtue of the spring portions which project laterally from the longitudinal axis. The major problem with this form of tie strip is the reliance on the mechanical properties of the spring portions correctly to expand and contract laterally during the threading process and subsequently to return to a latching state following insertion.